#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int Fib(int n)
{
	int a = 1; int b = 1;
	int c;
	if (n >= 3)
	{
		while (n >= 3)
		{
			c = a + b;
			a = b; b = c;
			n--;
		}
	}
	else
		c = a * n;
	return c;
}
int main()
{
	int ret, n;
	scanf("%d", &n);
	ret = Fib(n);
	printf("%d", ret);
	return 0;
}